First language acquisition is a hallmark of normative human development. A substantial body of research suggests that language learning is facilitated by the ability to track statistical regularities in linguistic input. Research during the current project period clearly demonstrates that infants are powerful statistical learners. However, the relevance of these abilities to the learning problems presented in infants' linguistic environments remains poorly understood. The research proposed in this application will test specific hypotheses concerning infant statistical language learning, focusing on how infants make use of statistical information. Specific Aim One is to determine which surface statistics infants can use given natural language input. Specific Aim Two is to determine how the statistics of sound sequences in real speech influence word learning. Specific Aim Three is to determine whether infants' on-line language processing is affected by statistical information. The results of the research proposed in this competing continuation application will promote positive developmental outcomes by expanding our understanding of the learning mechanisms underlying normative development. Individuals who are less facile at statistical learning may be at risk for developmental language disorders. Subsequent research will use the outcome of these studies to motivate investigations including populations of young children at risk for atypical language development.